Developing Device Staged Drive Gear Prevents Developer Clogging

The patent applies preliminary action by having the drive input gear be selectively coupled to either the first drive gear or the second drive gear, but not both simultaneously. This staged approach allows one developer conveyor to start rotating before the other, preventing pressure buildup that would occur if both were driven simultaneously. The selective coupling ensures that developer is gradually introduced into the lifting area rather than all at once, eliminating clogging and aggregation risks.

The patent applies asymmetry by configuring the supply screw and stirring screw to rotate in the same direction rather than opposite directions. This asymmetric configuration, combined with the selective coupling mechanism, ensures that developer is evenly distributed during the lifting process. The same-direction rotation prevents developer from accumulating at the lower side of the lifting area, achieving balanced developer distribution between the upper and lower containing portions.

The patent applies preliminary action by implementing a staged startup sequence where the drive input gear is selectively coupled to one drive gear before the other. This ensures that one developer conveyor begins rotating and establishes initial developer flow before the second conveyor starts. This sequential activation prevents pressure spikes and maintains developer uniformity, avoiding aggregation and clogging that would result from simultaneous startup.